High-temperature proton exchange membrane with toughness and strength and preparation method of high-temperature proton exchange membrane
By performing surface ionization and cross-linking treatment on high-temperature proton exchange membranes, the problem of mechanical property degradation caused by phosphoric acid doping was solved, and stable operation and high power density of ultrathin films at high temperatures were achieved.
Patent Information
- Application Number
- CN202511048328.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-12-12
AI Technical Summary
Existing high-temperature proton exchange membranes exhibit significantly reduced mechanical properties after phosphoric acid doping, making it difficult to find a balance between membrane thickness and mechanical properties, which affects the power density of the battery.
By subjecting the polybenzimidazole membrane to surface ionization and cross-linking treatment, a cross-linked structure is formed only on the membrane surface, enhancing mechanical properties while maintaining the phosphoric acid doping level and proton conductivity.
Stable operation of ultrathin films at high temperatures was achieved, improving the power density and mechanical properties of the battery, reducing the film thickness, and maintaining proton conductivity.
Smart Images
Figure CN121108550A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-temperature proton exchange membrane fuel cells, and more particularly to a high-temperature proton exchange membrane with both toughness and strength, and a method for preparing the same. Background Technology
[0002] High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have wide applications in energy and transportation. The HT-PEM, as a core component, plays a crucial role in isolating gases and transporting protons, requiring the membrane to maintain good mechanical stability during operation. Polybenzimidazole (PBI) membranes are currently the mainstream material for HT-PEMs, but they require doping with phosphoric acid (PA) to conduct protons. However, high PA doping can induce a strong plasticizing effect, significantly reducing the membrane's mechanical properties and hindering cell assembly. Membrane thickness, as one of the main factors affecting power density, is often inversely proportional to power density; that is, a lower membrane thickness results in a higher power density, but a lower membrane thickness also means worse mechanical properties. Traditional enhancement methods struggle to find a balance between membrane thickness and mechanical properties, making it difficult to achieve high power density.
[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-temperature proton exchange membrane with both toughness and strength and a method for preparing the same, in order to solve the problem that existing high-temperature proton exchange membranes will undergo strong plasticization after being subjected to the plasticizing effect of phosphoric acid, which will significantly reduce the mechanical properties of the membrane.
[0005] The technical solution of the present invention is as follows:
[0006] In a first aspect, the present invention provides a method for preparing a high-temperature proton exchange membrane that combines toughness and strength, comprising the following steps in sequence:
[0007] The polybenzimidazole membrane is placed in NaOH aqueous solution or HCl aqueous solution, heated to 60-80℃, and kept at that temperature for 1-2 hours to obtain a polybenzimidazole membrane with surface ionization.
[0008] The surface-ionized polybenzimidazole membrane is placed in a crosslinking agent and heated to 60-85℃ for 30-90 minutes to obtain a surface-crosslinked polybenzimidazole membrane.
[0009] The surface-crosslinked polybenzimidazole membrane is placed in phosphoric acid, heated to 120-160℃ and kept at that temperature for 24-48 hours to obtain the high-temperature proton exchange membrane that combines toughness and strength.
[0010] Optionally, the polybenzimidazole film is prepared by casting.
[0011] Optionally, the mass percentage concentration of the NaOH aqueous solution or HCl aqueous solution is 1-5%.
[0012] Optionally, before placing the ionized polybenzimidazole membrane into the crosslinking agent, it undergoes the following steps: wiping dry, washing with ethanol 2-3 times, and drying.
[0013] Optionally, before placing the surface-crosslinked polybenzimidazole membrane into phosphoric acid, the following steps are performed: wipe dry, wash with ethanol 2-3 times, and dry.
[0014] Optionally, the crosslinking agent is an ethanol solution of 1,4-dibromomethylbenzene or γ-(2,3-epoxypropoxy)propyltrimethoxysilane.
[0015] Optionally, the mass percentage concentration of 1,4-dibromomethylbenzene in the ethanol solution of 1,4-dibromomethylbenzene is 3-8%.
[0016] Optionally, the ethanol solution of 1,4-dibromomethylbenzene is prepared by the following method: adding 1,4-dibromomethylbenzene to ethanol, heating to 60-85°C and stirring for more than 24 hours until the 1,4-dibromomethylbenzene is fully dissolved.
[0017] In a second aspect, the present invention provides a high-temperature proton exchange membrane that combines toughness and strength, prepared by the above-described preparation method.
[0018] Beneficial Effects: This invention provides a method for preparing a high-temperature proton exchange membrane with surface crosslinking enhancement. The resulting high-temperature proton exchange membrane is thin and possesses advantages such as high tensile strength and high elongation at break. Since the crosslinking enhancement occurs only on the surface, the PA doping level and proton conductivity of the high-temperature proton exchange membrane are guaranteed, while the mechanical properties of the membrane are effectively improved. This is beneficial for achieving ultrathin membrane operation at high temperatures and for increasing battery power density.
[0019] This method is simple, stable, and inexpensive, and ultimately exhibits a fairly high power density. Attached Figure Description
[0020] Figure 1 This is a flowchart illustrating the preparation process of the high-temperature proton exchange membrane of the present invention, which combines toughness and strength.
[0021] Figure 2 The image shows a comparison of the XRD patterns of the surface crosslinked film in Example 1 and the surface crosslinked film after 4 μm of surface was removed.
[0022] Figure 3 This is a schematic diagram comparing the different solubilities of the surface crosslinked film in N-methylpyrrolidone in Example 1.
[0023] Figure 4 The images show a comparison of the different solubilities of the surface crosslinked film in N-methylpyrrolidone in Example 1.
[0024] Figure 5 The images show a comparison of the high-temperature proton exchange membrane (PBI) before and after oxidation of the non-surface crosslinked PBI membrane and the high-temperature PBI membrane of Example 1. (a) shows the non-surface crosslinked PBI membrane before oxidation, (c) shows the non-surface crosslinked PBI membrane after oxidation, (b) shows the high-temperature proton exchange membrane of Example 1 before oxidation, and (d) shows the high-temperature proton exchange membrane of Example 1 after oxidation.
[0025] Figure 6 The graphs show the polarization curves and power density curves for Example 1. Detailed Implementation
[0026] This invention provides a high-temperature proton exchange membrane with both toughness and strength, and a method for preparing the same. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0027] To ensure that the high-temperature proton exchange membrane, which combines toughness and strength, can operate normally at high temperatures, the mechanical properties of the membrane need to be enhanced, and the power density of the battery can be increased by reducing the membrane thickness.
[0028] This embodiment provides a method for preparing a high-temperature proton exchange membrane that combines toughness and strength, such as... Figure 1 As shown, the steps are as follows in sequence:
[0029] S1. Place the polybenzimidazole (PBI) membrane in an aqueous solution of NaOH or HCl, heat it to 60-80℃, and keep it at that temperature for 1-2 hours to obtain a PBI membrane with ionized surface.
[0030] S2. Place the surface-ionized PBI film into a crosslinking agent, heat it to 60-85℃ and keep it at that temperature for 30-90 minutes (e.g., 30 minutes, 60 minutes, 90 minutes) to obtain a surface-crosslinked PBI film.
[0031] S3. Place the surface-crosslinked PBI membrane into phosphoric acid (PA), heat it to 120-160℃ (e.g., 120℃, 130℃, 140℃, 150℃, 160℃) and keep it at that temperature for 24-48h (e.g., 24h, 36h, 48h) to obtain the high-temperature proton exchange membrane that has both toughness and strength.
[0032] In this embodiment, in step S1, the PBI membrane is added to an aqueous solution of NaOH or HCl, which ionizes the secondary amine groups on the molecular chains of the PBI membrane surface, facilitating subsequent reaction with the crosslinking agent. In step S2, the crosslinking agent reacts with the surface-ionized molecular chains of the PBI membrane, forming a crosslinked structure that is only formed on the surface. Because the crosslinking only occurs on the surface, the PA doping level and proton conductivity of the high-temperature proton exchange membrane are ensured, while the mechanical properties of the membrane are effectively improved. This is beneficial for achieving ultrathin film operation at high temperatures and for increasing battery power density. The crosslinked PBI membrane can reduce membrane thickness and increase power density.
[0033] In one embodiment, the PBI film is prepared by a casting method. Since the casting method for preparing PBI films is a mature technology and not the focus of this invention, it will not be described in detail here.
[0034] In some embodiments, the mass percentage concentration of the NaOH or HCl aqueous solution is 1-5%. Too high or too low a concentration will affect the surface ionization of the membrane, thus impacting the degree of subsequent crosslinking; generally, lower concentrations lead to lower subsequent crosslinking.
[0035] In one embodiment, before placing the ionized PBI membrane into the crosslinking agent, the following steps are performed: wiping dry, washing with ethanol 2-3 times, and drying.
[0036] In one embodiment, before placing the surface-crosslinked PBI film into the PA, the following steps are performed: wiping dry, washing with ethanol 2-3 times, and drying.
[0037] In some embodiments, the crosslinking agent is an ethanol solution of 1,4-dibromomethylbenzene or γ-(2,3-epoxypropoxy)propyltrimethoxysilane.
[0038] In some embodiments, the mass percentage concentration of 1,4-dibromomethylbenzene in the ethanol solution of the 1,4-dibromomethylbenzene is 3-8%, for example, 3%, 4%, 5%, 6%, 7%, or 8%.
[0039] In some embodiments, the ethanol solution of 1,4-dibromomethylbenzene is prepared by adding 1,4-dibromomethylbenzene to ethanol, heating to 60-85°C and stirring for more than 24 hours until the 1,4-dibromomethylbenzene is fully dissolved.
[0040] It should be noted that in this embodiment, the crosslinking agent 1,4-dibromomethylbenzene is fully dissolved in ethanol, which can prevent uneven crosslinking.
[0041] In a second aspect, the present invention provides a high-temperature proton exchange membrane that combines toughness and strength, prepared by the above-described preparation method.
[0042] The present invention will be further described below with reference to specific embodiments.
[0043] Example 1
[0044] 1. Prepare a 5% NaOH aqueous solution.
[0045] 2. Prepare an ethanol solution of 1,4-dibromomethylbenzene: Add 1g of 1,4-dibromomethylbenzene to ethanol, heat to 60℃ and stir for 24 hours to ensure that the 1,4-dibromomethylbenzene is fully dissolved, and prepare a 5% ethanol solution of 1,4-dibromomethylbenzene.
[0046] 3. A method for preparing a high-temperature proton exchange membrane that combines toughness and strength, comprising the following steps:
[0047] S1. Prepare PBI membrane by casting method. Place the membrane in a prepared 5% NaOH aqueous solution, heat to 80℃, and keep warm for 1 hour.
[0048] S2. Then remove the membrane, wipe it dry, wash it twice with ethanol, and then dry it in an oven. Place the membrane in a pre-prepared 5% ethanol solution of 1,4-dibromomethylbenzene, heat it to 60°C and keep it at that temperature for 1 hour before removing it.
[0049] S3. Wash twice with ethanol and then dry. Place the dried membrane in PA, heat to 160℃ and hold for more than 24 hours to complete PA doping.
[0050] The surface-crosslinked PBI film obtained in Example 1 after step S2 is designated CL-60; the surface of the surface-crosslinked PBI film obtained in Example 1 after step S2 is removed by sanding with sandpaper to remove 4 μm, exposing the uncrosslinked PBI inside, and this is designated M-CL-60; CL-60, M-CL-60, and PBI are subjected to XRD tests, and the results are as follows. Figure 2 As shown. From Figure 2 As can be seen, the diffraction angle of CL-60 obtained after surface crosslinking has shifted significantly, indicating that the molecular chain distance has decreased, representing successful crosslinking. The peak formed by the surface-crosslinked film M-CL-60 after surface grinding is basically at the same position as the peak of PBI, indicating that the interior still contains PBI molecular chains and no crosslinking has occurred.
[0051] The surface-crosslinked PBI film obtained in Example 1 after step S2 was placed in N-methylpyrrolidone and allowed to stand at 80°C for 48 hours. No dissolution was observed. After cutting open the surface-crosslinked PBI film obtained in Example 1 after step S2, it was placed in N-methylpyrrolidone (NMP) and allowed to stand at 80°C for 48 hours. It was observed that the PBI in the middle was dissolved by N-methylpyrrolidone, while the surface layer remained intact. This is because the surface crosslinking layer is highly dense, preventing NMP from dissolving it. However, after cutting, the exposed PBI in the middle was dissolved by NMP, while the surface crosslinking layer was preserved. A schematic diagram is shown below. Figure 3 , Figure 4 As shown.
[0052] The surface-crosslinked PBI film and the non-surface-crosslinked PBI film obtained in Example 1 after S2 were immersed in Fenton's reagent for 96 hours. The results are as follows. Figure 5 As shown. Figure 5 In the diagram, (a) shows the PBI membrane before oxidation (without surface crosslinking), (c) shows the PBI membrane after oxidation (without surface crosslinking), (b) shows the high-temperature proton exchange membrane of Example 1 before oxidation, and (d) shows the high-temperature proton exchange membrane of Example 1 after oxidation. Figure 5 It can be seen that the high-temperature protons that were not surface-crosslinked after oxidation developed pores, while the surface-crosslinked PBI film obtained in Example 1 remained intact after oxidation, indicating that the surface crosslinking layer helps to improve the oxidation stability of the film.
[0053] The polarization curve and power density curve of Example 1 were tested, and the results are as follows: Figure 6 As shown, the high-temperature proton exchange membrane of Example 1, which combines toughness and strength, achieves a power density of 1700 mW·cm⁻¹. -2 .
[0054] Measurements showed that the high-temperature proton exchange membrane with both toughness and strength obtained in Example 1 had a thickness reduced to 13 μm. After being assembled into a battery, it maintained good airtightness and stability at 160°C and with an applied back pressure of 0.2 MPa.
[0055] The high-temperature proton exchange membrane obtained in Example 1, which combines toughness and strength, has a PA doping rate as high as 280%.
[0056] After doping with phosphoric acid, the high-temperature proton exchange membrane obtained in this embodiment, possessing both toughness and strength, exhibits a tensile strength of 15.4 MPa (compared to 5.5 MPa for the original PBI), an elongation at break of 112.9% (compared to 62.9% for the original PBI), and a proton conductivity of 123.7 mS / cm at 160 °C. -1 (The original PBI was 21.3 mS cm) -1 ).
[0057] Therefore, the high-temperature proton exchange membrane obtained in Example 1, which combines toughness and strength, has excellent performance and application potential.
[0058] Example 2
[0059] 1. Prepare a 5% HCl aqueous solution.
[0060] 2. A method for preparing a high-temperature proton exchange membrane with both toughness and strength, comprising the following steps: Preparing a PBI membrane by a casting method; immersing the membrane in a prepared 5% HCl aqueous solution, heating to 60°C, holding for 1 hour, and then removing the membrane; wiping the membrane dry, washing it twice with ethanol, and then drying it in an oven; immersing the membrane in γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), heating to 80°C, holding for 1 hour, removing it, washing it twice with ethanol, and then drying it; immersing the dried membrane in PA, heating to 160°C, and holding for at least 24 hours to complete PA doping.
[0061] The high-temperature proton exchange membrane obtained in this embodiment, which combines toughness and strength, also has a high power density, reaching 823 mW / cm². -2 However, the power density of the high-temperature proton exchange membrane obtained in Example 2 is lower than that of the membrane obtained in Example 1 because the membrane thickness (35 μm) of Example 2 is greater than that of the membrane obtained in Example 1 (13 μm).
[0062] In summary, this invention provides a method for preparing a high-temperature proton exchange membrane with surface crosslinking enhancement. The resulting high-temperature proton exchange membrane has the advantages of high tensile strength and high elongation at break. Since the crosslinking enhancement only occurs on the surface, the PA doping level and proton conductivity of the high-temperature proton exchange membrane are guaranteed, which is beneficial to improving the power density of the battery.
[0063] This method is simple, stable, and inexpensive, and ultimately exhibits a fairly high power density.
[0064] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A method for preparing a high-temperature proton exchange membrane that combines toughness and strength, characterized in that, The steps are as follows in sequence: The polybenzimidazole membrane is placed in NaOH aqueous solution or HCl aqueous solution, heated to 60-80℃, and kept at that temperature for 1-2 hours to obtain a polybenzimidazole membrane with surface ionization. The surface-ionized polybenzimidazole membrane is placed in a crosslinking agent and heated to 60-85℃ for 30-90 minutes to obtain a surface-crosslinked polybenzimidazole membrane. The surface-crosslinked polybenzimidazole membrane is placed in phosphoric acid, heated to 120-160℃ and kept at that temperature for 24-48 hours to obtain the high-temperature proton exchange membrane that combines toughness and strength.
2. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 1, characterized in that, The polybenzimidazole film was prepared by casting.
3. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 1, characterized in that, The mass percentage concentration of the NaOH aqueous solution or HCl aqueous solution is 1-5%.
4. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 1, characterized in that, Before placing the ionized polybenzimidazole membrane into the crosslinking agent, it undergoes the following steps: wiping dry, washing with ethanol 2-3 times, and drying.
5. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 1, characterized in that, Before placing the surface-crosslinked polybenzimidazole membrane into phosphoric acid, the following steps are performed: wipe dry, wash with ethanol 2-3 times, and dry.
6. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 1, characterized in that, The crosslinking agent is an ethanol solution of 1,4-dibromomethylbenzene or γ-(2,3-epoxypropoxy)propyltrimethoxysilane.
7. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 6, characterized in that, The ethanol solution of 1,4-dibromomethylbenzene has a mass percentage concentration of 3-8% for 1,4-dibromomethylbenzene.
8. The method for preparing a high-temperature proton exchange membrane with both toughness and strength according to claim 7, characterized in that, The ethanol solution of 1,4-dibromomethylbenzene was prepared by the following method: 1,4-dibromomethylbenzene was added to ethanol, and the temperature was raised to 60-85℃ and stirred for more than 24 hours until the 1,4-dibromomethylbenzene was fully dissolved.
9. A high-temperature proton exchange membrane possessing both toughness and strength, characterized in that, Prepared by the preparation method according to any one of claims 1-8.